1. Field of the Invention
The invention relates to a cooling apparatus and a cooling method for an internal combustion engine that includes an electric water pump and an electric fan.
2. Description of the Related Art
A radiator, which cools a coolant for an internal combustion engine, is provided with an electric fan that maintains or assists the cooling performance of the radiator. The electric fan is operated when the temperature of the coolant is higher than a predetermined value. The coolant is circulated between the internal combustion engine and the radiator by a water pump. The water pump is generally operated using an engine output. The flow rate of the water pump is changed in synchronization with a change in an engine speed. Therefore, when the engine speed is low, the flow rate is low.
Accordingly, for example, a cooling apparatus described in Japanese Patent No. 2767995 includes a first water pump that is operated using an engine output; and a second water pump that is operated by an electric motor. When the engine speed is low, and the flow rate of the first water pump is insufficient, the second water pump is operated to compensate for the insufficiency.
The electric water pump and the electric fan consume electric power when the electric water pump and the electric fan are operated. Therefore, unless the electric water pump and the electric fan are controlled taking into account the efficiency of cooling the coolant, for example, the electric power consumed in the vehicle may be unnecessarily increased. Such an unnecessary increase in the consumed electric power may lead to, for example, an increase in the operating load of the alternator, which adversely affects the fuel efficiency of the internal combustion engine.